Boyd Alexander, From the Niger to the Nile, Vol. II, p. 238. London, 1907.
Haxthausen, Studien, Vol. I, p. 309. Die ländliche Verfassung Russlands, pp. 3, 7. Leipzig, 1866.
Ratzel, History of Mankind, Vol. II, pp. 79-83. London, 1896-1898. J. Wappaüs, Handbuch der Geographie und Statistik des ehemaligen spanischen Mittel- und Sud-Amerika, pp. 978-980, 1019. Leipzig, 1863-1870.
Ratzel, History of Mankind, Vol. II, pp. 206-208. London, 1896-1898.
Nordenskiold, Voyage of the Vega, pp. 60, 156, 452. New York, 1882. Alexander P. Engelhardt, A Russian Province of the North, pp. 291-295. London, 1899.
Ibid., pp. 83, 88-91.
Ratzel, History of Mankind, Vol. III, pp. 166-167. London. 1896-1898.
James Bryce, Impressions of South Africa, p. 107. New York, 1897.
Herodotus, Melpomene, 19, 46.
Thomas Hodgkin, Italy and Her Invaders, Vol. I, p. 262. Oxford, 1892.